Purely from the perspective of a user, pikes are longer( ten foot+) , less mobile, generally heavier , and rely on mass tactics. Singly they are near worthless and have limited utility. Drilled well, they are near impentrable to cavalry and in a charge it would fully suck to face a wall of Landsknecht.

A spear can be very small ( assegai, which is actually almost a partisan) or longer than a man ( insert Braveheart joke), though usually not by too much. Some were able to be used well with one hand, others not. Heavy ones like the Greek dory were capable of very hard thrusting strikes, most lighter ones might have been used to slash as much as thrust (it's a knife on a stick, mate).

In between is a horseman's lance, designs of which flourished in the 14th century. This would have been a pure thrusting weapon unless comparatively short. That one pound blade on an 8 ft pole generates ( calculating noises) four billion pounds of swing weight ( approximately) that the user has to control, and wrists only get just so strong.

TLDR: pokey things, sometimes slashy things, of various lengths.

A follow-up question: Is it true that it's harder to retract a pike? And thus your typical pike formation couldn't produce as many quick stabs as spears and that is why zweihanders were able to counter the pikes?

Or is the whole premise a silly idea? How else could the zweihanders effectively counter the pikes - as is often described?

Definitions are fuzzy, but we can probably agree to this much: a pike is a spear which is long enough that it requires two hands.

The main trade-off is a shield. A Greek hoplite, Saxon fyrd, or similar spearman, with a shield in his left hand, has excellent protection against slings and most bows, and some protection against javelins, franciscas, and crossbows. If adequately trained, they can form a shield wall, trading mobility for additional protection.

A pike phalanx, without shields, has to rely on their armor (supposedly, pikes held up at a 45° angle helped deflect some missiles, too, but I'm skeptical that this was effective). Some armies had success with silk armor, but for the most part light strong armor requires metal. Metal was expensive, especially before the Renaissance, when better smelting techniques and proto-mass production made "munition armor" reasonably cheap.

The upside to pikes is reach. With an overall length of five to six meters, compared to two or three for most one-handed spears, you could put three or four sharp bits in front of each soldier instead of two. Approaching a formation of disciplined pikemen from the front was almost suicidal. Greatswords and polearms were used to try to hack into pike phalanxes, but with little success. The best counter was to flank them or use powerful ranged weapons - harquebuses or muskets.

So getting back to your question: pikes gave soldiers more reach, making them even stronger against other infantry and cavalry. The cost was abandoning shields. For the most part, until crossbows and metal armor became common around 1200 to 1300, having a shield was indispensable. After that, shields were less effective and better armor was more effective, so it became worthwhile to forgo a shield to get greater offensive capability.

This lasted for a couple centuries, with "pike and shot" and "tercio" formations, but as guns got better the pikemen became more vulnerable: only very heavy armor could protect you from .65 caliber muskets. These eventually did away with pike blocks, especially after bayonets made the musket an adequate anti-cavalry weapon.

Most polearms were fundamentally spears with extra edges. These could be useful, but in a formation thrusts are preferred over swings, and so they often just added weight and expense for little gain.

Outside of actual warfare, neither weapon was common for dueling or civilian wear, for the obvious reason that they get in the way when you're sitting down for a pint. Pikes in particular need a lot of room. Spears, on the other hand, work just fine in close quarters, such as in boarding actions on ships (cf. "spontoon" and "half-pike"). Note that a spear can do everything a quarterstaff can do, plus stick 'em with the pointy end.

Does that answer your question? I could sprinkle some links in here, but I'm on mobile, and honestly Wikipedia is a perfectly good place to learn more about any of these topics.